Lubrication oil supply structure

ABSTRACT

A main journal  25   a  of a crank-shaped swinging shaft  25  which swings in a range of a predetermined angle is supported by bearing metals  51  and  52  each divided into two pieces. In supplying a lubrication oil through an oil bore  51   b  in the bearing metal  51  to a sliding surface of the main journal  25   a  and to inlet openings of lubrication oil passages P 1  and P 2  of the swinging shaft 25 open to the sliding surface, the inlet openings of the lubrication oil passages P 1  and P 2  of the swinging shaft  25  are designed so that they do not move past division portions  55  of the bearing metals  51  and  52  upon swing of the swinging shaft  25  in the range of the predetermined angle. Therefore, it is possible to prevent the lubrication oil to be supplied to the lubrication oil passages P 1  and P 2  from leaking from the division portions  55  of the bearing metals 51 and 52, thereby reliably lubricating a pin journal  25   b  of the swinging shaft  25  by the lubrication oil supplied from the lubrication oil passages P 1  and P 2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubrication oil supply structure inwhich a lubrication oil passage formed within a rotary shaft or aswinging shaft is open to a journal which is supported by a bearingmember divided into a plurality of pieces, and relates to a lubricationoil supply structure which is applied to a control shaft of an engine.

2. Description of the Related Art

There is a variable compression ratio engine known from Japanese PatentApplication Laid-open No. 2003-322036, which comprises a crankshaftwhose main journal is rotatably supported in an engine block, a controlshaft whose main journal is supported in the engine block so as to swingin a range of a predetermined angle, a lower link swingably supported atits intermediate portion on a pin journal of the crankshaft, an upperlink connecting one end of the lower link to a piston, and a controllink which connects the other end of the lower link to a pin journal ofthe control shaft.

With this variable compression ratio engine, the control shaft is swungby an actuator to move the control link vertically, thereby changing themotion-restraining condition of the lower link to change the strokecharacteristic including the position of a top dead center of a piston,thereby controlling the compression ratio of the engine as desired.

When a journal of a shaft is supported by a bearing metal divided into aplurality of pieces, and a portion of a lubrication oil for lubricatinga sliding surface of the journal is supplied to other portions to belubricated through a lubrication oil passage formed within the shaft,the pressure on portions in the vicinity of division portions of abearing metal divided into a plurality of pieces is reduced due to theleakage of the lubrication oil. Therefore, there is a possibility thatwhen an inlet opening of the lubrication oil passage moves to face thedivision portions, the amount of the lubrication oil supplied from aninner peripheral surface of the bearing metal to the lubrication oilpassage is decreased, so that it is impossible to sufficiently lubricatethe other portions to be lubricated.

Especially in the case where the opening of the lubrication oil passagestops for a certain period of time at a location opposed to the divisionportions of the bearing metal, there is a possibility that a state ofthe decreased amount of lubrication oil continues to cause a lubricationdeficiency.

SUMMARY OF THE INVENTION

The present invention has been accomplished with the above circumstancein view, and it is an object of the present invention to ensure thatlubrication oil can be reliably supplied to a journal of a rotary shaftor a swinging shaft supported by a bearing member divided into aplurality of pieces.

In order to achieve the above object, according to a first feature ofthe present invention, there is provided a lubrication oil supplystructure in which a lubrication oil passage formed within a rotaryshaft is open to a journal which is supported by a bearing memberdivided into a plurality of pieces, wherein an opening of thelubrication oil passage of the rotary shaft is designed so that theopening does not stop at division portions of the bearing member.

With the above arrangement, in the lubrication oil supply structure inwhich the journal, to which the lubrication oil passage formed withinthe rotary shaft is open, is supported by the bearing member dividedinto the plurality of pieces, the opening of the lubrication oil passageof the rotary shaft is designed so that the opening does not stop at thedivision portions of the bearing member. Therefore, it is possible toprevent by the simple arrangement the lubrication oil from leaking fromthe division portions to cause the lubrication deficiency.

Further, according to a second feature of the present invention, thereis provided a lubrication oil supply structure in which a lubricationoil passage formed within a swinging shaft, which swings in a range of apredetermined angle, is open to a journal which is supported by abearing member divided into a plurality of pieces, wherein an opening ofthe lubrication oil passage of the swinging shaft is designed so thatthe opening does not stop at division portions of the bearing member.

With the above arrangement, in the lubrication oil supply structure inwhich the journal, to which the lubrication oil passage formed withinthe swinging shaft which swings in the range of the predetermined angleis open, is supported by the bearing member divided into the pluralityof pieces, the opening of the lubrication oil passage of the swingingshaft is designed so that the opening does not stop at the divisionportions of the bearing member. Therefore, it is possible to prevent bythe simple arrangement the lubrication oil from leaking from thedivision portions to cause the lubrication deficiency.

Furthermore, according to a third feature of the present invention,there is provided a lubrication oil supply structure comprising: acrankshaft whose main journal is rotatably supported in an engine block;a control shaft whose main journal is supported in the engine block soas to swing in a range of a predetermined angle; a lower link swingablysupported on a pin journal of the crankshaft; an upper link connectingthe lower link to a piston; and a control link which connects the lowerlink or the upper link to a pin journal of the control shaft, the mainjournal of the control shaft being supported by a bearing metal dividedinto a plurality of pieces, a lubrication oil being supplied through thebearing metal to a sliding surface of the main journal of the controlshaft and to an inlet opening of a lubrication oil passage which isformed within the control shaft and open to the sliding surface of themain journal of the control shaft, wherein the range of swing of thecontrol shaft is determined so that the inlet opening of the lubricationoil passage of the control shaft does not move past division portions ofthe bearing metal divided into the plurality of pieces.

With the above arrangement, the lower link is swingably supported on thepin journal of the crankshaft and connected to the piston through theupper link, and the lower link or the upper link is connected to the pinjournal of the control shaft through the control link. Therefore, it ispossible to change the motion-restraining condition of the lower link tochange the stroke characteristic of the piston by swinging the controlshaft in the range of the predetermined angle about the main journal tomove the control link vertically.

The main journal of the control shaft is supported by the bearing metaldivided into the plurality of pieces, and when the lubrication oil issupplied through the bearing metal to the sliding surface of the mainjournal and to the inlet opening of the lubrication oil passage in themain journal opening to the sliding surface, the inlet opening of thelubrication oil passage of the control shaft is designed so that theopening does not move past the division portions of the bearing metalupon swing of the control shaft in the range of the predetermined angle.Therefore, it is possible to prevent the lubrication oil to be suppliedto the lubrication oil passage from leaking from the division portionsof the bearing metal to cause the lubrication deficiency. Especially, itis possible to excellently maintain the supply of the lubrication oil tothe pin journal of the control shaft to which a large load is applied bya combustion pressure, leading to a smooth movement of each link.

According to a fourth feature of the present invention, in addition tothe third feature, the lubrication oil passage of the control shaft isdivided into a first lubrication oil passage open to the main journal ofthe control shaft, and a second lubrication oil passage open to the pinjournal of the control shaft, the first and second lubrication oilpassages being formed to intersect each other at a predetermined angleas viewed in an axial direction of the control shaft.

With the above arrangement, the lubrication oil passage of the controlshaft is comprised of the first and second oil passages intersectingeach other at the predetermined angle, the first lubrication oil passageis formed to be open to the main journal, and the second lubrication oilpassage is formed to be open to the pin journal. Therefore, it ispossible to easily design the inlet opening so that the opening does notstop at the division portions of the first and second bearing metals,while connecting together the main journal and the pin journal by thefirst and second lubrication oil passages.

A control shaft 25 in embodiments corresponds to the rotary shaft or theswinging shaft of the present invention; a main journal 25 a in theembodiments corresponds to the journal of the present invention; firstand second bearing metals 51 and 52 in the embodiments correspond to thebearing metal or the bearing member of the present invention; and firstand second lubrication oil passages P1 and P2 in the embodimentscorrespond to the lubrication oil passage of the present invention.

The above and other objects, features and advantages of the inventionwill become apparent from the preferred embodiments which will bedescribed with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 9 show a first embodiment of the present invention, whereinFIG. 1 is a vertical sectional view of a variable compression ratioengine (in a state of a high compression ratio); FIG. 2 is a view takenalong a line 2-2 in FIG. 1; FIG. 3 is a view taken along a line 3-3 inFIG. 1; FIG. 4 is a view taken in a direction of an arrow 4 in FIG. 1;FIG. 5 is a vertical sectional view of the variable compression ratioengine (in a state of a low compression ratio); FIG. 6 is an enlargedsectional view of an area indicated by 6 in FIG. 1 (in the state of thehigh compression ratio); FIG. 7 is a sectional view taken along a line7-7 in FIG. 6; FIG. 8 is an exploded perspective view of a bearingmetal; and FIG. 9 is an enlarged sectional view of Part 9 in FIG. 5 (inthe state of the low compression ratio).

FIGS. 10 and 11 show a second embodiment of the present invention,wherein FIG. 10 is a view similar to FIG. 6 (in a state of a highcompression ratio); and FIG. 11 is a view similar to FIG. 9 (a state ofa low compression ratio).

DESCRIPTION OF PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described withreference to FIGS. 1 to 9.

First, a variable compression ratio engine which is one example of avariable stroke characteristic engine in which positions of a top deadcenter and a bottom dead center of a piston are changeable, will bedescribed as the first embodiment of the present invention.

As shown in FIGS. 1 to 4, the variable compression ratio engine Eincludes an engine block 13 to which a cylinder block 11 and a crankcase12 are coupled. A cylinder head 14 and a head cover 15 are coupled to anupper portion of the cylinder block 11. An oil pan 16 is formed in alower portion of the crankcase 12. A main journal 17 a of a crankshaft17 is rotatably supported on parting faces of the cylinder block 11 andthe crankcase 12. An intermediate portion of a substantially triangularlower link 18 is pivotally supported so as to swing on a pin journal 17b eccentric from the main journal 17 a.

A piston 21 is slidably received in a cylinder sleeve 20 mounted in thecylinder block 11. An upper link 22 (a connecting rod) is pivotallysupported at its upper end on the piston 21 through a piston pin 23, andat its lower end on one end of the lower link 18 through a first pin 24.A main journal 25 a of a crank-shaped control shaft 25 is pivotallysupported, via a cap 27 fastened to the crankcase 12 by bolts 26, 26 soas to swing, on a lower surface of the crankcase 12 laterally eccentricfrom the position of the crankshaft 17. A control link 28 includes abody 28 a and a cap portion 28 b fastened to a lower end of the body 28a by bolts 29, 29. The body 28 a is pivotally supported at its upper endon the other end of the lower link 18 through a second pin 30. A pinjournal 25 b of the control shaft 26 is pivotally supported between alower end of the body 28 a and the cap portion 28 b. The control shaft25 swings in a range of a predetermined angle (for example, 120°) by anactuator (not shown) mounted at one end of the control shaft 25.

An intake port 32 and an exhaust port 33 are open into a combustionchamber 14 a formed in a lower surface of the cylinder head 14. Anintake valve 34 for opening and closing the intake port 32 and anexhaust valve 35 for opening and closing the exhaust port 33 are mountedin the cylinder head 14. The intake valve 34 is opened and closed by anintake camshaft 36 through an intake rocker arm 37. The exhaust valve 35is opened and closed by an exhaust camshaft 38 through an exhaust rockerarm 39.

As shown in FIGS. 6 and 8, half-cylindrical first and second bearingmetals 51 and 52 are mounted on parting faces 50 of the crankcase 12 andthe cap 27, respectively, which clamp the main journal 25 a of thecontrol shaft 25. Oil grooves 51 a and 52 a for spreading a lubricationoil to an outer peripheral sliding surface of the main journal 25 a areformed in inner peripheral surfaces of the first and second bearingmetals 51 and 52. An oil bore 51 b is formed in the first bearing metal51 supported on the side of the crankcase 12. An oil reservoir 12 a isformed in the crankcase 12 so as to face the oil bore 51 b in the firstbearing metal 51, and is connected to a lubrication oil pump (not shown)through oil passages 12 b and 12 c.

On the other hand, a first lubrication oil passage P1 and a secondlubrication oil passage P2 are formed in the control shaft 25. The firstlubrication oil passage P1 is open to the outer peripheral slidingsurface of the main journal 25 a, and the second lubrication oil passageP2 is formed to intersect the first lubrication oil passage P1 and opento an outer peripheral sliding surface of the pin journal 25 b.Half-cylindrical first and second bearing metals 53 and 54 are mountedrespectively to the body 28 a and the cap portion 28 b of the controllink 28 supporting the pin journal 25 b of the control shaft 25. Thesecond lubrication oil passage P2 is open into oil grooves 53 a and 54 acircumferentially formed in inner peripheral surfaces of the first andsecond bearing metals 53 and 54.

The operation of the first embodiment of the present invention havingthe above-described arrangement will be described below.

The actuator is driven in accordance with the operational state of theengine E, whereby the control shaft 25 connected to the actuator isrotated to any position between a position shown in FIG. 1 and aposition shown in FIG. 5. In the position shown in FIG. 1, the pinjournal 25 b is located below the main journal 25 a of the control shaft25. Therefore, the control link 28 is pulled down, so that the lowerlink 18 is swung in a clockwise direction about the pin journal 17 b ofthe crankshaft 17, whereby the upper link 22 is pushed up to raise theposition of the piston 21, thereby bringing the engine E into a state ofa high compression ratio.

On the other hand, in the position shown in FIG. 5, the pin journal 25 bis located above the main journal 25 a of the control shaft 25.Therefore, the control link 28 is pushed up, so that the lower link 18is swung in a counterclockwise direction about the pin journal 17 b ofthe crankshaft 17, whereby the upper link 22 is pulled down to lower theposition of the piston 21, thereby bringing the engine E into a state ofa low compression ratio.

In this way, the control link 28 is moved up and down by the swing ofthe control shaft 25, thereby changing the motion-restraining conditionof the lower link 18 to change the stroke characteristic including theposition of the top dead center of the piston 21. In this manner, thecompression ratio of the engine E is controlled as desired.

As shown in FIGS. 6 to 9, the lubrication oil is supplied to the oilreservoir 12 a through the oil passages 12 c and 12 b in the crankcase12 in order to lubricate the main journal 25 a and the pin journal 25 bof the control shaft 25 during operation of the engine E, and flows fromthe oil bore 51 b of the first bearing metal 51 among the first andsecond bearing metals 51 and 52 supporting the main journal 25 a of thecontrol shaft 25 into the oil grooves 51 a and 52 a in the innerperipheral surface of the first and second bearing metals 51 and 52,thereby lubricating the sliding surface of the main journal 25 a.

A portion of the lubrication oil supplied to the oil bore 51 b in thefirst bearing metal 51 flows from the first lubrication oil passage P1formed in the control shaft 25 via the second lubrication oil passage P2to reach the sliding surface of the pin journal 25 b, and then flowsinto the oil grooves 53 a and 54 a in the inner peripheral surfaces ofthe first and second bearing metals 53 and 54 supporting the pin journal25 b, thereby lubricating the sliding surface of the pin journal 25 b.

A portion of the lubrication oil supplied to the oil grooves 51 a and 52a in the inner peripheral surfaces of the first and second bearingmetals 51 and 52 leaks from division portions 55, 55 of the first andsecond bearing metals 51 and 52 via the parting surfaces 50 of thecrankcase 12 and the cap 27. Therefore, a reduction of hydraulicpressure is inevitable in the vicinity of the division portions 55, 55.Therefore, there is a possibility that when an inlet opening of thefirst lubrication oil passage P1 moves past the division portions 55, 55in the process of the swing of the control shaft 25, or when the inletopening of the first lubrication oil passage P1 stops at the divisionportions 55, 55, the amount of the lubrication oil supplied to the firstlubrication oil passage P1 is decreased to cause a lubricationdeficiency to the pin journal 25 b.

In the present embodiment, however, even if the control shaft 25 isswung between a high compression ratio position shown in FIG. 6 and alow compression ratio position shown in FIG. 9, the position of theinlet opening of the first lubrication oil passage P1 of the mainjournal is determined so that the opening is not aligned with thedivision portions 55, 55 of the first and second bearing metals 51 and52, namely, the inlet opening of the first lubrication oil passage P1cannot stop at the division portions 55, 55 of the first and secondbearing metals 51 and 52 in the process of the reciprocal swing of thecontrol shaft 25. Therefore, it is possible to minimize the leakage ofthe lubrication oil from the division portions 55, 55 and supply thelubrication oil having a sufficient pressure to the first lubricationoil passage P1, thereby reliably lubricating the pin journal 25 b.Especially, it is possible to excellently maintain the supply of thelubrication oil to the pin journal 25 b of the control shaft 25 to whicha large load is applied by a combustion pressure, leading to a smoothmovement of each link.

To ensure a sufficient vertical stroke of the control link 28, the pinjournal 25 b is required to move vertically in Figures across theparting faces 50 of the crankcase 12 and the cap 27. Therefore, if thefirst and second lubrication oil passages P1 and P2 are replaced by asingle straight lubrication oil passage, an inlet opening of such alubrication oil passage inevitably moves past the division portions 55,55 of the first and second bearing metals 51 and 52 for the main journal25 a. In the present embodiment, however, it is possible to easilyprevent the inlet opening of the first lubrication oil passage P1, intowhich the lubrication oil flows, from moving past the division portions55, 55 of the first and second bearing metals 51 and 52, by forming thefirst and second lubrication oil passages P1 and P2 intersecting eachother at a predetermined angle in the control shaft 25.

A second embodiment of the present invention will now be described withreference to FIGS. 10 and 11.

In the above-described first embodiment, the oil reservoir 12 a and thelubrication oil passages 12 b and 12 c for supplying the lubrication oilto the main journal 25 a of the control shaft 25 are formed in thecrankcase 12, but in the second embodiment, an oil reservoir 27 a andlubrication oil passages 27 b and 27 c are formed in the cap 27, and thearrangement of the other components is the same as that of the firstembodiment.

Also in the second embodiment, when the control shaft 25 is locatedbetween the high compression ratio position shown in FIG. 10 and the lowcompression ratio position shown in FIG. 11, the inlet opening of thefirst lubrication oil passage P1 cannot move past the division portions55, 55 of the first and second bearing metals 51 and 52, therebyachieving an effect same as that of the first embodiment.

Although the embodiments of the present invention have been described,various modifications in design may be made without departing from thesubject matter of the invention.

For example, the variable compression ratio engine has been described inthe embodiments, but one or both of the compression ratio and thedisplacement of the engine can be changed by changing the dimensions ofvarious portions in the same structure. The present invention isapplicable to this kind of variable stroke characteristic engine.

The application of the present invention is not limited to a swingingshaft such as the control shaft 25, and the present invention is alsoapplicable to a rotary shaft rotatable at a rotational angle exceeding360°. Also in this case, the leakage of lubrication oil can be minimizedby arranging the rotary shaft so that the inlet opening of the firstlubrication oil passage P1 does not stop at the division portions 55, 55of the first and second bearing metals 51, 51.

Further, in the embodiments, the control link 28 is connected to thelower link 18, but the present invention is also applicable to avariable stroke characteristic engine in which the control link 28 isconnected to the upper link 22.

Furthermore, in the embodiments, the opening of the first lubricationoil passage P1 is the inlet for the lubrication oil, but may be anoutlet for the lubrication oil.

1. A lubrication oil supply structure in which a lubrication oil passageformed within a rotary shaft is open to a journal which is supported bya bearing member divided into a plurality of pieces, wherein an openingof the lubrication oil passage of the rotary shaft is designed so thatthe opening does not stop at division portions of the bearing member. 2.A lubrication oil supply structure in which a lubrication oil passageformed within a swinging shaft, which swings in a range of apredetermined angle, is open to a journal which is supported by abearing member divided into a plurality of pieces, wherein an opening ofthe lubrication oil passage of the swinging shaft is designed so thatthe opening does not stop at division portions of the bearing member. 3.A lubrication oil supply structure comprising: a crankshaft whose mainjournal is rotatably supported in an engine block; a control shaft whosemain journal is supported in the engine block so as to swing in a rangeof a predetermined angle; a lower link swingably supported on a pinjournal of the crankshaft; an upper link connecting the lower link to apiston; and a control link which connects the lower link or the upperlink to a pin journal of the control shaft, the main journal of thecontrol shaft being supported by a bearing metal divided into aplurality of pieces, a lubrication oil being supplied through thebearing metal to a sliding surface of the main journal of the controlshaft and to an inlet opening of a lubrication oil passage which isformed within the control shaft and open to the sliding surface of themain journal of the control shaft, wherein the range of swing of thecontrol shaft is determined so that the inlet opening of the lubricationoil passage of the control shaft does not move past division portions ofthe bearing metal divided into the plurality of pieces.
 4. A lubricationoil supply structure according to claim 3, wherein the lubrication oilpassage of the control shaft is divided into a first lubrication oilpassage open to the main journal of the control shaft, and a secondlubrication oil passage open to the pin journal of the control shaft,the first and second lubrication oil passages being formed to intersecteach other at a predetermined angle as viewed in an axial direction ofthe control shaft.